A typical powered hammer or hammer drill, such as the one disclosed in EP1157788, may include a body in which is mounted an electric motor and a hammer mechanism. A tool holder may be mounted on the front of the body which holds a cutting tool, such as a drill bit or a chisel. The hammer mechanism may include a slideable ram reciprocatingly driven by a piston, the piston being reciprocatingly driven by the motor via a set of gears and a crank mechanism or wobble bearing. The ram may repeatedly strike the end of the cutting tool via a beat piece. When the only action on the tool bit is the repetitive striking of its end by the beat piece, the hammer drill is operating in a hammer only mode.
Certain types of hammer drills also comprise a rotary drive mechanism which enable the tool holder to rotatingly drive the cutting tool held within the tool holder. This can be in addition to the repetitive striking of the end of the cutting tool by the beat piece (in which case, the hammer drill is operating in a hammer and drill mode) and/or as an alternative to the repetitive striking of the end of the cutting tool by the beat piece (in which case, the hammer drill is operating in a drill only mode).
Hammer drills are supported by the operator using one or more handles. In one example of a hammer drill, there is a rear handle attached to the rear of the body of the hammer drill, at the opposite end of the body to where the tool holder is mounted. The operator pushes the cutting tool into a work piece by pushing the rear handle towards the body, which in turn pushes the body and the cutting tool towards the work piece.
Hammer drills tend to generate vibration, in particular, by operation of the hammer mechanism. This vibration is transferred to the hands of the operator holding the handles of the hammer drill, particularly through the rear handle. This can result in the injury of the hands of the operator. As such, it is desirable to minimize the effect of vibration experienced by the hands of the operator. This is achieved by reducing the amount by which the handle vibrates. One method is to reduce the amount of vibration produced by the whole hammer drill. Another method is to reduce the amount of vibration transferred from the body of the hammer drill to the rear handle. For example, EP 1529603 discloses a dampening mechanism for a rear handle by which the amount of vibration transferred from the body to the handle is reduced.